The prediction of CAT (clear air turbulence) which results from wind shear, has been the subject of considerable effort. Such CAT generally occurs within areas of the atmosphere in which the tropopause or an inversion layer lie. The tropopause is the intersection of the troposphere and the stratosphere, and is an altitude at which air temperature increases with altitude. An inversion layer generally is a layer of air wherein the temperature of the air increases with altitude and which is embedded in a much deeper mass of air wherein temperature decreases with altitude. In these situations, CAT may occur in patches over an area of perhaps 100 kilometers which lies within an inversion layer of a width of perhaps 1000 kilometers, and a depth of 1000 to 3000 feet (300 to 1000 meters). Various devices have been proposed for avoiding CAT, as by the use of infrared or microwave radiometers to view regions directly in front or to scan to the left or right of the direction of flight of the aircraft, so that the aircraft can fly around areas of potential CAT or the pilot can know when to brace for a possible encounter with CAT. However, it is often impractical to fly around a large area where CAT might occur because of the wide area in which patches of CAT may be present, while knowledge as to the approach of a possible CAT region is often of limited benefit if avoidance cannot be accomplished. A system which facilitates the avoidance of regions of CAT, with minimal change in the original intended flight path, would be of great value.